The present invention relates generally to the application of energy to materials and biological tissue, and specifically to the application of electromagnetic energy to soft and hard tissue in order to create a desired predetermined esthetic pattern or a perforation pattern to allow a substance to penetrate surface layer barrier.
Applications of optical sources for drilling various material including biological soft and hard tissue has been investigated over the past thirty years. Such applications included the use of lasers to remove material, cut tissue or precisely machine wafers in electronic applications.
The simplest way to generate a predictable drilled hole pattern in a material is to use an amplitude mask consisting of the required spatial configuration. Such a mask allow variations in the amplitude of the impinging energy source to be transmitted. For this reason such a mask is called an amplitude mask. It can be used in the optical case, in a near-field configuration and then a scaled up version of the desired focal pattern are made to create the pattern in a larger scale. Such a scheme, however, suffers from the drawback that most of the energy is not utilized but is wasted on absorption in the mask, where such energy is wasted as heat and does not serve a useful purpose of creating the patterns.
An alternative method employs means for focusing and stirring the beam to the desired spot. This method has the advantage of conserving laser energy but the disadvantage of sequential drilling which means longer processing time.
Another way of avoiding the waste of energy associated with amplitude masks is employing means for spatially re-distributing the energy so that the beam energy is split up into several beams and interacts simultaneously with multiple locations on the target. One such method of re-distributing the energy in space is, in the case of electromagnetic energy, employing a phase plate. A phase plate is constructed with various optical thickness (OT) over its cross-section and is placed in the path of the laser beam. The electromagnetic beam having transverse through different sections of the phase plate undergoes different phase delays. It is possible to design the phase plate (or other means for changing the wave front energy distribution of the wave front) in such a way that the original beam energy is focused on the target to form any desirable distribution pattern.
The technology of optical phase plate can be very useful to several areas of medicine. In general, the ability to divide a single beam output into several beamlets can revolutionize many applications of lasers in medicine and biology, save time, cost and in many cases, improve or provide for the execution of procedures that hitherto were not possible using a single beam techniques.
Some of the envisioned applications are:
Transdermal delivery: The stratum corneum in the human skin provides the principal barrier that limits the percutaneous penetration of topical drugs to blood vessels. This barrier can be penetrated in a very precise and minimally destructive way through the application of ultrashort pulse lasers. As we have shown previously, lasers are highly efficient in converting optical energy to remove biomedical tissue. In a similar manner, the human nail plates (of either fingers or toes) or the skin stratum corneum can be precisely ablated to form a predetermined perforation pattern which is ideal for accessing the visualized nail bed, thus allowing the coupling of drugs to the body circulatory system. The hole pattern can be generated through any number of laser sources. However, as we have shown in previous studies, because the USPL is capable of extreme precision and minimal collateral damage, we anticipate that it will even be possible to generate hole pattern of sufficiently large total surface removal yet individual holes small enough so that external organic as well as inorganic contaminant penetration is significantly minimized.
Currently, there are no other competing methods to generate controlled skin penetration other than tape-stripping which is both painful and exposes very large surfaces of the skin.
A second class of applications, is the generation of perforation pattern to circumvent and treat a common yet persisting problems in the fields of preventive and restorative dentistry. Here enhanced bond strength is conventionally obtained through phosphoric acid etching. A hole pattern ranging from 10 xcexcm to 100 xcexcm in diameter (0.1 to 2 mm deep, although optimal depth will be determined experimentally and will vary with age and tooth conditions) that would serve to enhance bond strength in a reliable predictable and reproducible manner and will be significantly superior to conventional methods. Such enhanced bonding will be used in laminated vaneers coating of tooth anterior where significant leakage and caries formation occurs in the juvenile population. Drilling an xe2x80x9canchorxe2x80x9d pattern for massive amalgam fillings where currently a single screw is used to secure the large mass to the drilled hole bottom. Since current cavity preparation techniques also require a wedge shape cavity for enhancing filling retention, considerable amount of healthy tissue must be removed. Consequently, minimizing the amount of material removed while inducing superior bond strength are the two main objective of our proposed LDPG. Finally, enhanced retention of dental crowns and bridges can also be generated using the same LDPG techniques. Bond strength and filling retention properties are expected to increase dramatically.
Additional applications of controlled hole pattern generation are:
ENTxe2x80x94Middle ear bone surgeryxe2x80x94creating a hole pattern for attachment of prostases, transfer of prostese motion for restoration of mechanical vibration-transmitting chain.
Orthopedicsxe2x80x94Arthroscopic surgery (partial neniscectomy, synovectomy, chondroplasty); cartilage and tendon removal; bone incisions; microperforation, resurfacing and texturing of cartilage, tendon and bone, preparation of surface for restorative device implantation.
Angioplasty, Arheroscleratic plaque removal and preparation of vascular surfaces for stent insertion
Laser Treatment of Heart Diseases
TANSMYOCARDIAL LASER RE-VASCULARIZATION (TMRL) is a technique that brings blood directly to oxygen-deprived tissue from INSIDE the heart itself by drilling array of holes in the heart muscle. The phase plate approach enables drilling many holes simultaneously, with big effective f# giving a possibility to drill cm long channels without any additional equipment (fiberoptics etc).
In general, this technique can be used for crater pattern generation, micro perforation, precise ablation, sculpting, resurfacing, and texturing of all inorganic and organic materials and biological tissue (soft and hard).
Arterial blockages are a common cause of coronary artery disease, the No. one killer worldwide. According to the American Heart Association more than 1.5 million Americans suffer heart attacks each year. One-third die as a result.
The TMLR takes a different approachxe2x80x94instead of bypassing or widening a clogged artery, blood is brought directly to oxygen-deprived tissue from INSIDE the heart itself!
Current experimental procedures use Carbon-dioxide laser to vaporize tiny holes through the heart""s outer walls, creating channels that bring blood directly to oxygen-starved tissue. Others have utilized TMLR using a Holmium:YAG or excimer lasers. Yet others have tested fiberoptics-based Intraoperative Tansmyocardial Revascularization (ITMR) for both surgical and catheter-based percutaneous (minimally invasive) TMLR methods.
TMLR has several advantages: operating time is ONLY 1-2 hours Operation is performed on a BEATING heart (by synchronizing the laser firing with electronic signal from the heartxe2x80x94EKG machine.) The laser drill 20 to 30 1 mm diameter holes through the muscular wall of the left ventricle.
Blood fills the channels, bringing in oxygen to the starved tissue. The exterior wall of the heart heals quickly.
A key to the success of the operation is knowing where to aim the laser. This is accomplish by injecting the patient with a radioactive chemical that is readily taken by the health heart cells. On an imaging scan blood deficient stand out in sharp contrast to healthy tissue. With the oxygen-deprived tissue identified, the surgeon makes a 4-inch incision between the ribs, exposing the left ventricle. A computer synchronized with the patient heartbeats waits for the less than {fraction (1/20)} second interval between each beat. This interval is used to fire the laser. Examination of hearts of patients who underwent the procedure showed that the interior surfaces of the laser-bored channels shows that they grow a layer of the same type of cells that line natural blood vessels. Blood vessels were also shown to develop from the SIDES of the laser-drilled channels.
Already (with trial laser procedures) hospital stay after the laser surgery may average six days or even less, as opposed to 11 days for a bypass operation. It is also expected that laser operation and smaller holes will reduce healing time. Drilling multiple channels will limit thermal damage, more closely mimic natural vascularization and may allow us to control the rate of channel closure. Using phase plates for simultaneous whole drilling or rapid beam manipulations in combination with light-based systems further limit and control thermal damage and would further shorten healing times.
Finally, the laser-drilled channels have formed walls similar to those found in healthier blood vessels. (i.e. the channel actually becomexe2x80x94new blood vessels!) Clearly, the rapid rate of drilling using multiple beamlets will drastically reduce both procedure and healing time.
An energy source is focused down to power densities sufficient for ablating a fingernail without producing painful heat or damage to the underlying layers. By controlling the spot size, energy, and pulse duration a pattern may be formed in the target. The depth and shape of the pattern can be varied from a very light surface modification to penetration through the entire nail. Two computer-controlled scanners steer the laser beam to form an arbitrary pattern. Modulation of the laser beam can be accomplished electronically or mechanically. The pattern of drilled holes thus formed may be utilize to perforate of a barrier layer to allow delivery of a substance across a the barrier layer.